GAS TURBINE WITH A VIBRATION DAMPER

Description

[0001] The present disclosure concerns prevention of damage to blades in rotors of gas turbines. The invention specifically concerns a gas turbine engine.

[0002] In the field of gas turbines it is well known to deliver streams of fluid (typically bled from a compressor stage) to other parts of the gas turbine engine. This fluid may then be used for cooling components (the materials of which might otherwise be incapable of withstanding the temperatures to which they are exposed) and/or sealing (e.g. creating a pressure differential across a potential leakage path).

[0003] Taking a specific example, it is known to cool cavities located between adjacent blade shanks radially inward of their platforms with cooling fluid. The cooling fluid supplied typically enters a pre-chamber axially upstream of these cavities. From there a proportion of the fluid may be channelled radially outwards to seal a potential leakage path between the blade platforms and an annulus wall. The remainder of the fluid is however incident into the cavities, the stream into each cavity being substantially unidirectional. This unidirectional stream impinges on the cavity walls, and where it does so tends to cause a build-up of deposits and/or corrosion. The stream, while providing a useful function in cooling and ventilating the cavities, may be of significant detriment to the maintenance cycle times and longevity of the blades in view of the mentioned deposits.

[0004] Various solutions have been considered to this problem, including changes to the shape and/or composition of the cavity walls and changes to the architecture of the cooling fluid supply and/or the source of the cooling fluid. Generally however each of these options carries a penalty in terms of performance and/or manufacturing cost.

[0005] US 3,266,771 discloses a turbine having a rotor disc, a plurality of angularly spaced apart rotor blades having root portions mounted in the rotor disc, each of said rotor blades having a platform and a radially extending shank. The platform is disposed radially outwardly of and connected to the respective root portion by the shank. A plurality of flexible channel members, substantially U-shaped in section are provided. Each flexible channel member has side walls connected by a base wall, each of said channel members having the free ends of its side walls in spring loaded engagement with the circumference of said rotor disc and its side walls spaced from the shanks of adjacent blades. Said flexible channel members are urged by centrifugal force during rotation of said rotor disc so that the base wall of the same engages the radially inner surface of each platform to thereby dampen vibration of the rotor blades which occur in operation.

[0006] US 2013/0064668 A1 discloses a rotor blade assembly for a rotor of a gas turbine engine having an axis of rotation includes a shank portion formed from a ceramic matrix composite CMC) material. The rotor blade assembly also includes a platform portion formed from a substantially similar CMC material as that of the shank portion. The platform portion is coupled to the shank portion. The platform portion and the shank portion cooperate to at least partially define two opposing side portions of the rotor blade assembly. The opposing side portions are angularly separated with respect to the axis of rotation. The rotor blade assembly further includes a damper retention apparatus. The damper retention apparatus is coupled to the shank portion. The damper retention apparatus includes at least one angled bracket apparatus extending toward a circumferentially adjacent rotor blade assembly.

[0007] GB 2411697 A discloses a turbine rotor disc provided with a coolant path for conveying coolant towards a cavity defined above a rim section of the disc and between adjacent blade roots. A flow diverter comprising a recessed portion causes coolant flow to remain adjacent the rim section. The diverter may be U-shaped with arms, and be coated on its inner surfaces with low heat emissivity materials. The diverter may support or be integral with a damper member and the recessed portion may be provided with perforations to provide impingement cooling.

[0008] US 2013/0323031 A1 discloses damper for a turbine rotor assembly of a gas turbine engine is disclosed. The damper includes a width dimension, a height dimension, and a length dimension and a forward plate. The damper further includes an aft plate that is larger than the forward plate along the width and height dimension and having a lower portion including two legs extending in the height dimension. The damper also includes a longitudinal structure extending in the length dimension and connecting the forward plate and the aft plate

[0009] According to a first aspect of the invention there is provided a gas turbine engine as set out in the appended claim 1. Optional features are set out in the claims dependent thereto.

[0010] The suction side of the shank may be particularly vulnerable to corrosion as a result of direct impingement by the cooling fluid stream thereon. The suction side may also be particularly vulnerable to the build-up of deposits found in the cooling fluid stream. The use of the damper with the deflector nose may however prevent direct impingement of a cooling fluid stream on parts or all of the suction side, limiting or preventing damage and/or build-ups. Modification of the relatively inexpensive damper to provide the deflector nose may provide a cost-effective method of dealing with this issue.

[0011] For simplicity and clarity features such as dampers, cavities and blades tend to be discussed in the singular throughout this document. Nonetheless it will be appreciated that multiple examples of such features (including their sub-features) may be beneficially comprised in a single rotor.

[0012] In some embodiments the cooling fluid delivery system is arranged to deliver the cooling fluid incident into the cavity in a substantially axial direction. Thus it may be that the cooling fluid is delivered from in front of the cavity rather than, for instance, from radially inward of it. Consequently the cooling fluid incident on the suctions side of the shank may be incident from an axial direction.

[0013] In some embodiments the longitudinal axis of the main body of the damper is parallel to a wedge face of the platform with which it is in contact. The wedge face is the face of the platform adjacent and opposing a similar platform face of an adjacent blade.

[0014] The incident stream of cooling fluid may travel at an angle to the plane described above as a consequence of rotation of the rotor. An axially travelling incident stream of cooling fluid may therefore be considered angled towards incidence on the suction side of the shank partially defining the cavity and away from incidence on the pressure side of the shank of the adjacent blade also partially defining the cavity. In this case the plate oriented as described may close a window that would otherwise permit direct incidence on an area of the suction surface by the stream. It should be further noted that because the smallest dimension of the panel is in the circumferential direction, unnecessary blocking of the stream of cooling fluid into the cavity may be minimised. For this reason the deflector nose may also be narrower than the main body of the damper, which may be optimised in terms of its dimensions for vibration damping.

[0015] In some embodiments the deflector nose is substantially equidistant the pressure and suction sides partially defining the cavity. The deflector nose may therefore be considered to extend radially through the circumferential centre of the cavity.

[0016] In some embodiments the main body of the damper is located adjacent one or more of the platforms and the nose extends radially inwards from the main body into the cavity.

[0017] In some embodiments the nose extends for substantially the full radial extent of the cavity.

[0018] In some embodiments the damper is adapted to balance the impact of the deflector nose on the centre of gravity of the damper. The damper may for example further comprise a tail arranged to balance the deflector nose such that the centre of gravity of the damper is located as required for effective damping.

[0019] In some embodiments the cooling fluid delivery system comprises a bleed from a gas turbine engine compressor and ducting for delivery of bled fluid.

[0020] Embodiments of the invention will now be described by way of example only, with reference to the Figures, in which:

Figure 1 is a sectional side view of a gas turbine engine;

Figure 2 is a side view of part of a prior art turbine rotor;

Figure 3a is a side view of a damper in accordance with an embodiment of the invention;

Figure 3b is a side view of a damper in accordance with an embodiment of the invention;

Figure 4 is a front axially downstream view of part of a turbine rotor according to an embodiment of the invention.

[0021] With reference to Figure 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, a low-pressure turbine 17 and an exhaust nozzle 18. A nacelle 20 generally surrounds the engine 10 and defines the intake 12.

[0022] The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the high-pressure compressor 14 and a second air flow which passes through a bypass duct 21 to provide propulsive thrust. The high-pressure compressor 14 compresses the air flow directed into it before delivering that air to the combustion equipment 15.

[0023] In the combustion equipment 15 the air flow is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high and low-pressure turbines 16, 17 before being exhausted through the nozzle 18 to provide additional propulsive thrust. The high 16 and low 17 pressure turbines drive respectively the high pressure compressor 14 and the fan 13, each by suitable interconnecting shaft.

[0024] Referring now to Figure 2 an exemplary prior art portion of a turbine rotor is shown. A blade is generally provided at 30 and comprises a main portion 32 and a shank 34 radially inward of the main portion 32. The main portion 32 and shank 34 are separated by a platform 36. The blade 30 has a suction side (not shown) and a pressure side 38. The blade 30 extends radially outwards from a disc 40. Additional similar blades (not shown) are disposed circumferentially around and extending radially from the disc 40. The platform 36, in combination with the platforms of the additional blades, substantially seals a circumferential opening 42 in the inner wall 44 of a gas annulus 46.

[0025] Part of a fluid delivery system 48 including a pre-chamber 50 is also shown, providing a flow path to an interface between the platform 36 and the inner wall 44. The fluid delivery system 48 (again including the pre-chamber 50) also provides a flow path into a cavity 52. The cavity 52 is between the shank 34 of the pressure side 38 and the shank (not shown) of the suction side (not shown) of an adjacent blade (not shown). The cavity 52 is further defined by, and is radially inward of, the platform 36, and a similar platform (not shown) of the adjacent blade. As will be appreciated the pre-chamber 50 extends circumferentially, providing a fluid flow path to all cavities defined between adjacent blades around the rotor. Upstream of the pre-chamber 50, the fluid delivery system 48 comprises conduit and other channelling means (not shown) providing a fluid flow path to the pre-chamber 50 from a compressor bleed (not shown).

[0026] Seated adjacent and in contact with the platform is a vibration damper 54. The damper 54 is shielded from cooling fluid entering the cavity 52 by a lip 56 of the platform 36. Indeed in many embodiments the damper 54 is contained in a damper slot, formed in one or both adjacent platforms.

[0027] In use the fluid delivery system 48 provides cooling fluid to the cavity 52 and all similar cavities around the rotor. It also provides sealing fluid to the interface between the platform 36 and the inner wall 44, as well as to all similar interfaces around the rotor. In view of rotation of the rotor, an axially travelling stream of cooling fluid delivered via the pre-chamber 50 to the cavity 52 is incident upon a blade shank suction side partially defining the cavity 52. Where the stream impinges on the suction side it tends to cause corrosion and/or deposit build ups on the shank, reducing the efficiency with which the shank is cooled and reducing the life of the blade. The damper 54 meanwhile is a loose fit against the platform 36 and so tends to vibrate with any vibration of the blade 30, thereby causing friction and heating by which blade 30 vibration energy is dissipated. This blade vibration damping may be advantageous in preventing undesired aerodynamic effects and component wear.

[0028] Referring now to Figure 3a a vibration damper according to the present invention is generally shown at 60. The damper 60 has a main body 62. The main body 62 has a substantially consistent cross-sectional shape. Extending from one end of the main body 62 is a deflector nose 64. The deflector nose 64 is in the form of a flat plate, substantially rectangular in shape and thinner than the main body 62. The deflector nose 64 is of consistent thickness (although in other embodiments it may be tapered towards side distal to the main body 62). Extending from the other end of the main body 62 is a tail 66. In combination the main body 62, deflector nose 64 and tail 66 give the damper 60 a 'C' shape when viewed from the side. The deflector nose 64 and tail 66 are arranged such that the centre of gravity of the main body 62 is substantially at its centre. This may be of assistance in mounting the damper 60 and in allowing it to vibrate as desired to damp blade vibration. Both the deflector nose 64 and tail 66 are integral with the main body 62.

[0029] Referring briefly to Figure 3b an alternative vibration damper 70 according to an embodiment of the invention is shown. The vibration damper 70 is similar to the vibration damper 60, but a tail 72 of the vibration damper 70 is extended into a hook formation 74, which may assist in locating and securing the damper 70.

[0030] Referring now to Figure 4 a portion of a turbine rotor is generally shown at 80, the rotor being suitable for use in a gas turbine engine. The rotor 80 is similar to the rotor part of which was described with reference to Figure 2. The damper 54 has however been replaced with a damper in accordance with the present invention (such as those 60, 70 shown in Figures 3A and 3B). Consequently deflector noses 82 of dampers 84 extend radially inwards into respective cavities 86. Each deflector nose 82 extends for substantially the full radial extent of its respective cavity 86. Each deflector nose 82 is substantially equidistant pressure 88 and suction 90 sides of the shanks 92 of adjacent blades 94 which partially define the corresponding cavity 86. Further the deflector noses 82 are in the form of a thin, flat plate oriented so as to lie parallel to wedge faces 95 of the adjacent platforms. Each deflector nose 82 is also oriented so as to lie in a respective plane that is substantially radially extending and substantially parallel to the main rotation axis of the rotor. Consequently the deflector noses 82 equally bifurcate axially forward areas of their respective cavities 84. Because however each deflector nose 82 is of sufficient axial length to extend for only a proportion of the axial extent of the damper 84, axially rear portions of each cavity 86 are not bifurcated.

[0031] In use, a fluid delivery system (not shown) provides cooling fluid to the cavities 86 via a pre-chamber (not shown). In view of rotation of the rotor 80 (indicated by rotation direction 96), an axially travelling stream of cooling fluid delivered via the pre-chamber is incident towards the suction sides 90 of the blade shanks 92 partially defining the cavities 86 (as indicated by stream lines 98). The streams of cooling fluid are however prevented from impinging directly on the suction sides 90 by the deflector noses 82. In view of the positioning and axial and radial extent of each deflector nose 82, each blocks all direct flow paths to the respective suction side 90 from the direction of incidence of the respective cooling fluid stream. Further because the axial extent of each deflector nose 82 is the minimum necessary to deflect the stream of cooling fluid incident into the respective cavity 86 away from the suction side 90, mixing and circulation of the cooling fluid is not further inhibited in an axially rearward area of the cavity 86.

[0032] Dampers 84 therefore perform a double function of reducing deposits and corrosion of the suction sides 90 of the shanks while continuing to perform as a vibration damper.

[0033] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the scope of the invention as defined in the appended claims. By way of example the main body of the damper may be contained in a damper slot, formed in one or both adjacent platforms, optionally in the wedge faces, with the damper nose extending out of the damper slot and into the cavity.

Claims

1. A gas turbine engine comprising a rotor and a cooling fluid delivery system,

the rotor (80) comprising a disc and a plurality of blades (94) extending radially therefrom,

each blade having a suction side and a pressure side and comprising a shank (92), a platform and a main portion,

the main portion being radially outward of the shank (92) and separated therefrom by the platform, and where at least one cavity (86) is defined, each of said at least one cavity (86) being radially inward of the platforms and between a suction side (90) of the shank (92) of one blade and a pressure side (88) of the shank (92) of an adjacent blade,

and wherein the rotor (80) further comprises at least one damper (60, 70, 84), the damper (60, 70, 84) comprising a main body in contact with at least one of said one blade and said adjacent blade, the damper further comprising a deflector nose (64, 82),

the deflector nose (64, 82) extending from the main body into the cavity (86), wherein the deflector nose (64, 82) extends axially only along a forward portion of the axial extent of the damper main body and beyond the forward axial extent of the damper main body,

wherein the deflector nose comprises a plate oriented so as to lie parallel to a wedge face (95) of the blade platform with which the damper (60, 70, 84) is in contact, wherein the wedge face is a face of the platform adjacent and opposing a similar platform face of an adjacent blade, wherein the deflector nose is arranged so that in use it deflects a stream of cooling fluid incident into the cavity (86) delivered by the cooling fluid delivery system, away from the suction side (90) of the shank (92) partially defining the cavity (86).

2. A gas turbine engine according to claim 1, wherein the cooling fluid delivery system is arranged to deliver the cooling fluid incident into the cavity (86) in a substantially axial direction.

3. A gas turbine engine according to claim 1 or claim 2, wherein the longitudinal axis of the main body of the damper (60, 70, 84) is parallel to a wedge face (95) of the platform with which it is in contact.

4. A gas turbine engine according to any preceding claim, wherein the deflector nose (64, 82) is substantially equidistant from the pressure and suction (90) sides partially defining the cavity (86).

5. A gas turbine engine according to any preceding claim, wherein the main body of the damper (60, 70, 84) is located adjacent one or more of the platforms and the nose (64, 82) extends radially inwards from the main body into the cavity (86).

6. A gas turbine engine according to any preceding claim, wherein the deflector nose (64, 82) extends for substantially the full radial extent of the cavity (86).

7. A gas turbine engine according to any preceding claim, wherein the damper (60, 70, 84) is adapted to balance the impact of the deflector nose (64, 82) on the centre of gravity of the damper (60, 70, 84).

8. A gas turbine engine according to any preceding claim, wherein the cooling fluid delivery system comprises a bleed from a gas turbine engine compressor and ducting for delivery of bled fluid.

Ansprüche

1. Gasturbinentriebwerk, umfassend einen Rotor und ein Kühlfluid-Zufuhrsystem, wobei der Rotor (80) eine Scheibe und eine Vielzahl von sich radial davon erstreckenden Schaufeln (94) umfasst,

wobei jede Schaufel eine Saugseite und eine Druckseite aufweist und einen Schaft (92), eine Plattform und einen Hauptabschnitt umfasst,

wobei sich der Hauptabschnitt radial auswärts von dem Schaft (92) befindet und von dort durch die Plattform getrennt ist, und wobei mindestens ein Hohlraum (86) definiert ist, wobei sich jeder von dem mindestens einen Hohlraum (86) radial einwärts von den Plattformen und zwischen einer Saugseite (90) des Schafts (92) einer Schaufel und einer Druckseite (88) des Schafts (92) einer benachbarten Schaufel befindet, und wobei der Rotor (80) ferner mindestens einen Dämpfer (60, 70, 84) umfasst, wobei der Dämpfer (60, 70, 84) einen Hauptkörper in Kontakt mit mindestens einer von der einen Schaufel und der benachbarten Schaufel umfasst, wobei der Dämpfer ferner eine Ablenknase (64, 82) umfasst, wobei sich die Ablenknase (64, 82) vom Hauptkörper in den Hohlraum (86) erstreckt, wobei sich die Ablenknase (64, 82) axial nur entlang eines vorderen Abschnitts der axialen Erstreckung des Dämpferhauptkörpers und über die vordere axiale Erstreckung des Dämpferhauptkörpers hinaus erstreckt,

wobei die Ablenknase eine Platte umfasst, die ausgerichtet ist, um parallel zu einer Keilfläche (95) der Schaufelplattform zu liegen, mit der der Dämpfer (60, 70, 84) in

Kontakt ist, wobei die Keilfläche eine Fläche der Plattform ist, die einer ähnlichen Plattformfläche einer benachbarten Schaufel benachbart ist und gegenüberliegt, wobei die Ablenknase

so angeordnet ist, dass sie im Gebrauch einen in den Hohlraum (86) einfallenden Kühlfluidstrom, der von dem Kühlfluid-Zufuhrsystem zugeführt wird, weg von der Saugseite (90) des Schafts (92) ablenkt, die den Hohlraum (86) teilweise definiert.

2. Gasturbinentriebwerk nach Anspruch 1, wobei das Kühlfluid-Zufuhrsystem angeordnet ist, um das in den Hohlraum (86) einfallende Kühlfluid in einer im Wesentlichen axialen Richtung zuzuführen.

3. Gasturbinentriebwerk nach Anspruch 1 oder Anspruch 2, wobei die Längsachse des Hauptkörpers des Dämpfers (60, 70, 84) parallel zu einer Keilfläche (95) der Plattform ist, mit der sie in Kontakt steht.

4. Gasturbinentriebwerk nach einem der vorhergehenden Ansprüche, wobei die Ablenknase (64, 82) im Wesentlichen gleich weit von der Druck- und der Saugseite (90) entfernt ist, die den Hohlraum (86) teilweise definieren.

5. Gasturbinentriebwerk nach einem der vorhergehenden Ansprüche, wobei der Hauptkörper des Dämpfers (60, 70, 84) benachbart zu einer oder mehreren der Plattformen liegt und sich die Nase (64, 82) vom Hauptkörper radial nach innen in den Hohlraum (86) erstreckt.

6. Gasturbinentriebwerk nach einem der vorhergehenden Ansprüche, wobei sich die Ablenknase (64, 82) über im Wesentlichen die volle radiale Erstreckung des Hohlraums (86) erstreckt.

7. Gasturbinentriebwerk nach einem der vorhergehenden Ansprüche, wobei der Dämpfer (60, 70, 84) angepasst ist, um den Aufprall der Ablenknase (64, 82) auf den Schwerpunkt des Dämpfers (60, 70, 84) auszugleichen.

8. Gasturbinentriebwerk nach einem der vorhergehenden Ansprüche, wobei das Kühlfluid-Zufuhrsystem eine Anzapfung von einem Gasturbinentriebwerkskompressor und eine Leitung zum Zuführen von Zapffluid umfasst.

Revendications

1. Moteur à turbine à gaz comprenant un rotor et un système de distribution de fluide de refroidissement, le rotor (80) comprenant un disque et une pluralité d'aubes (94) s'étendant radialement à partir de celui-ci,

chaque aube possédant un côté aspiration et un côté pression et comprenant une tige (92), une plate-forme et une partie principale,

la partie principale étant radialement à l'extérieur de la tige (92) et séparée de celle-ci par la plate-forme, et où au moins une cavité (86) est définie, chacune desdites au moins une cavités (86) étant radialement à l'intérieur des plates-formes et entre un côté aspiration (90) de la tige (92) d'une aube et un côté pression (88) de la tige (92) d'une aube adjacente, et ledit rotor (80) comprenant en outre au moins un amortisseur (60, 70, 84), l'amortisseur (60, 70, 84) comprenant un corps principal en contact avec au moins l'une de ladite aube et de ladite aube adjacente, l'amortisseur comprenant en outre un nez de déflecteur (64, 82), le nez de déflecteur (64, 82) s'étendant à partir du corps principal dans la cavité (86), ledit nez de déflecteur (64, 82) s'étendant axialement uniquement le long d'une partie avant de l'étendue axiale du corps principal d'amortisseur et au-delà de l'étendue axiale avant du corps principal d'amortisseur,

ledit nez de déflecteur comprenant une plaque orientée de façon à être parallèle à une face de coin (95) de la plate-forme d'aube avec laquelle l'amortisseur (60, 70, 84) est en

contact, ladite face de coin étant une face de la plate-forme adjacente et opposée à une face de plate-forme similaire d'une aube adjacente, ledit nez de déflecteur

étant agencé afin que lors de l'utilisation, il dévie un flux de fluide de refroidissement incident dans la cavité (86) distribué par le système de distribution de fluide de refroidissement, loin du côté aspiration (90) de la tige (92) définissant partiellement la cavité (86).

2. Moteur à turbine à gaz selon la revendication 1, ledit système de distribution de fluide de refroidissement étant agencé pour distribuer le fluide de refroidissement incident dans la cavité (86) dans une direction sensiblement axiale.

3. Moteur à turbine à gaz selon la revendication 1 ou la revendication 2, ledit axe longitudinal du corps principal de l'amortisseur (60, 70, 84) étant parallèle à une face de coin (95) de la plate-forme avec laquelle il est en contact.

4. Moteur à turbine à gaz selon une quelconque revendication précédente, ledit nez de déflecteur (64, 82) étant sensiblement équidistant des côtés de pression et d'aspiration (90) définissant partiellement la cavité (86).

5. Moteur à turbine à gaz selon une quelconque revendication précédente, ledit corps principal de l'amortisseur (60, 70, 84) étant situé à côté d'une ou plusieurs des plates-formes et le nez (64, 82) s'étendant radialement vers l'intérieur à partir du corps principal dans la cavité (86).

6. Moteur à turbine à gaz selon une quelconque revendication précédente, ledit nez de déflecteur (64, 82) s'étendant sur sensiblement toute l'étendue radiale de la cavité (86).

7. Moteur à turbine à gaz selon une quelconque revendication précédente, ledit amortisseur (60, 70, 84) étant adapté pour équilibrer l'impact du nez de déflecteur (64, 82) sur le centre de gravité de l'amortisseur (60, 70, 84).

8. Moteur à turbine à gaz selon une quelconque revendication précédente, ledit système de distribution de fluide de refroidissement comprenant une purge provenant d'un compresseur de moteur à turbine à gaz et de canalisations pour la distribution de fluide de purge.

Drawing